fixing bugs in asynchronous tasks

rowers/tasks.py

@@ -1754,15 +1754,15 @@ def handle_updatefitnessmetric(user_id,mode,workoutids,debug=False,
 def handle_updatecp(rower_id,workoutids,debug=False,table='cpdata',**kwargs):
     columns = ['power','workoutid','time']
     df = getsmallrowdata_db(columns,ids=workoutids,debug=debug)
-    dfgrouped = df.groupby(['workoutid'])
 
-    if not df.empty:
-        maxt = 1.05*df['time'].max()/1000.
-    else:
-        maxt = 1000.
+    if df.empty:
+        return 0
+
+    maxt = 1.05*df['time'].max()/1000.
 
     logarr = datautils.getlogarr(maxt)
 
+    dfgrouped = df.groupby(['workoutid'])
 
     delta,cpvalue,avgpower = datautils.getcp(dfgrouped,logarr)